Molecular, Neurogenetic and Plastic Components of Food Related Behaviors in the Fruit Fly

Marla B. Sokolowski

University of Toronto

The question of how genes contribute to normal individual differences in behavior has captured our imagination for more than a century. Two fundamental questions come to mind: how do genes and their proteins act in the nervous system in order to cause individual differences in behavior? How do genes and their proteins act in response to the environment to affect normal individual differences in behavior? Understanding the connection between genotypic differences and changes in gene expression requires studies on genes that vary under natural conditions. The foraging (for) gene in Drosophila melanogaster is responsible for naturally occurring rover and sitter food search behavior. Animals homozygous for the sitter allele (fors) exhibit short foraging trails whereas those with a rover allele (forR) travel farther in search of food. The for gene encodes one of two cGMP-dependent protein kinases (PKG) in Drosophila. for transcript abundance and PKG activity levels are higher in rover adult heads and larval central nervous systems (CNSs) than in sitter heads and larval CNSs when the animals are well fed. When animals are removed from food for several hours rovers behave more sitter-like indicating that the genetically different rovers and sitters can exhibit plastic responses in their foraging behavior in response to environmental change. We show that changes in for gene expression parallel these plastic behavioral responses. Thus it appears that the PKG encoded by for may function in normal individual differences in behavior that arise from both: 1) differences in gene expression due to natural allelic variation and, 2) differences in gene expression due to environmentally induced changes in the behavioral state of an individual.